This file is responsible for bonus priests (clerics and druids) spells because of their wisdom:
Columns numerated from 1 to 7 indicates the priest spell book level
First column is the CRE's wisdom.
The crossing of them indicate how many bonus spells have priest creature with specified wisdom.

In BG2EE we have:

2DA V1.0
0
        1   2   3   4   5   6   7
13      1   0   0   0   0   0   0
14      2   0   0   0   0   0   0
15      2   1   0   0   0   0   0
16      2   2   0   0   0   0   0
17      2   2   1   0   0   0   0
18      2   2   1   1   0   0   0
19      3   2   1   2   0   0   0
20      3   3   1   3   0   0   0
21      3   3   2   3   1   0   0
22      3   3   2   4   2   0   0
23      3   3   2   4   4   0   0
24      3   3   2   4   4   2   0
25      3   3   2   4   4   3   1